It costs nothing to be nice to people when offering criticism.
There’s zero need to flame someone that wasn’t initially trying to flame in the first place, you can and should mention things of course if it bothers you but you can approach it as an adult and realise you have no idea who is behind that screen, or in real life are you also the type of person that screams at the people in line at a grocery store? No you only do that online because you don’t see the person behind so it’s easier to take out your anger but you can literally never know who is behind the screen.
Could be a kid, could be an older person, could be someone that just witnessed a hard life event, there’s no need to try to raise your low self esteem by acting tough and non “soy” to strangers online.

It’s not your job to teach them how to play, but you can remove yourself from people and situations that make you angry.
I too encountered my share of underleveled gray armour tanks who refused to use CDs and I do tell them that under these conditions, keeping him alive with wall to wall pulls is proving very difficult, but people usually either take it nicely back or they blame it on me for not healing them when one hit literally kills them and I could easily lose my s*it on that but it’s just not worth it, I know my actions, I looked hard over my job and I tried to help him, if he doesn’t want the help, me risking a ban is not worth it. If someone’s play style bothers you that much then just find a different party or learn some patience for your own good first, and theirs second, it goes hand in hand. Obviously this won’t get anywhere on a troll thread but eh.